This invention relates generally to impact drive sprinklers, and more particularly, to a simplified impact drive sprinkler constructed from relatively inexpensive components and having improved hydraulic flow characteristics.
Impact drive sprinklers in general are known in the art for use in applying irrigation water to crops, lawn areas, and the like. Such sprinklers typically include a sprinkler body mounted at the upper end of a water supply pipe or riser in a manner permitting rotation of the sprinkler body about the axis of the riser. A water flow path is formed within the sprinkler body for guiding a stream of water under pressure upwardly from the riser and then for turning the water stream in a generally outward and upwardly inclined direction for projection through a discharge nozzle. A spring-biased drive arm mounted on the sprinkler body is driven in an oscillatory manner by the projected water stream to impact the sprinkler body at a regular frequency for rotating the sprinkler body in small angular increments about the axis of the riser, whereby the projected water stream is swept over a circular region of soil for irrigation. If full circle rotation of the sprinkler body is not desired, the impact drive assembly can include a conventional reversing mechanism for periodically reversing the direction of rotation thereby permitting use of the sprinkler to irrigate within a selected arcuate region.
According to conventional manufacturing methods, the sprinkler body is formed from a rust-free or rust-resistant material such as brass or plastic by a casting or molding process wherein the material is poured or injected into a closed mold having an internal mold cavity conforming to the desired sprinkler body geometry. This type of manufacturing process, however, tends to be relatively costly, particularly with regard to the formation of the different molds for each sprinkler body configuration.
In a sprinkler body formed by casting or molding, the internal water flow path is typically defined by a pair of generally linear passages which intersect angularly with each other within the sprinkler body. These generally linear passages can be formed by use of internal cores which are positioned within the mold cavity prior to casting and then removed from the sprinkler body after it is separated from the mold. Alternatively, the generally linear passages can be formed by a drilling process. In either event, the intersecting passages form a relatively abrupt angular bend in the water flow path wherein the bend is not smoothly contoured for optimizing hydraulic flow with minimum turbulence. Instead, the bend is defined by a variety of surface irregularities, discontinuities, and interruptions which are inherent with the method of forming the intersecting passages. As a result, when sprinkler bodies of this general type are used, the water experiences substantial turbulence as it flows through the bend to reduce significantly the kinetic energy of the water stream projected from the discharge nozzle, thereby reducing correspondingly the range of the water stream and the soil area which can be irrigated. While this energy loss can be alleviated in part by the use of so-called straightener vanes positioned along the flow path immediately upstream of the nozzle, such straightener vanes increase the cost of the sprinkler and do not prevent at least some energy losses.
A further disadvantage encountered with conventional cast sprinkler bodies is that the spring-biased drive arm has a size and shape uniquely chosen to match a particular sprinkler body configuration. More specifically, the drive arm is typically mounted on the sprinkler body for oscillatory movement about the axis of the water supply riser and includes a deflector spoon shaped for appropriate interaction with a water stream having a particular trajectory. If it is desired, however, to manufacture an alternative sprinkler body wherein the trajectory of the projected water stream has a different angle of inclination, it is also necessary to manufacture an alternative drive arm shaped to match the new trajectory. Since these drive arms are normally manufactured by a casting or molding process, additional uniquely-shaped molds are required to thus further contribute significantly to the final cost of the sprinkler.
The present invention overcomes the problems and disadvantages of the prior art by providing an improved impact drive sprinkler wherein the sprinkler body is formed from an inexpensive length of tubing which is bent to a selected angle for projecting a water stream at a desired trajectory. Moreover, the tubular sprinkler body is adapted for use with a drive arm of substantially universal geometry regardless of the trajectory of the projected water stream, wherein the drive arm advantageously can be formed from inexpensive stamped metal parts.